Transformers are used extensively for current sensingbecause they can monitor currents with verylow power loss and they have wide bandwidth forgood waveform fidelity. Current transformers performwell in applications with symmetrical AC currentssuch as push-pull or full bridge convertertopologies. In single-ended applications, especiallyboost converters, problems can arise because ofthe need to accurately reproduce high duty factor,unipolar, waveforms. Unipolar pulses may saturatethe current transformer and, if this happens, overcurrent protection will be lost and, for current modecontrol, regulation will be lost and an over voltagecondition will result.